Electric sanding machine



DeC- 30, 1941, F. o. ALBERil-soN 21,267,781

ELECTRIC SANDING MACHINE Filed NOV. 9, 1939 2 Sheets-Sheet l C ELECTRIC SANDING MACHNE Filed Nov. 9, 1959 2 Sheets-Sheet 2 zaag/ae?? Patented Dec. 30, 1941 ELECTRIC SANDING ltIACHINE Frans O. Albertson,

Albertson & Company,

corporation of Iowa Sioux City, Iowa, assignor to Inc., Sioux City, Iowa, a

Application November 9, 1939, Serial No. 303,532

7 Claims.

The present invention relates to electric sanding machines, and is particularly concerned with electric sanding machines of the type having a motor, speed reducing gearing, and a driven shaft carrying a supporting pad and a sanding disc. In the sanding machines of the prior art, as exemplified in my prior patents, considerable trouble has been experienced with noisy gears, and there is considerable complaint from the users of such electric sanders on account of the unpleasant rattling or grinding noise of such sanding machines of the prior art, and the wear which takes place on the gears, due to the use to which the sanding machines are subjected.

In using such a sanding machine the sanding disc is applied to the work, and at such time a load is placed upon the motor, but the load is released at intervals, when the sanding machine is lifted from one point on the work to another, causing the pinion to slam back and forth against the teeth of the crown gear, and creating excessive rattle and noise.

It is found in devices of this type, which have been in use for some time, that there is just as much wear on the back of the teeth as there is on the load side. This shows the friction which is caused by abrupt changes in load, and such friction causes unnecessary heat, as well as noise, which are disadvantages in such a portable tool.

One of the objects of the invention is the provision of an improved electric sanding machine, having means for eliminating rigidity of contact or engagement between the driving and driven parts of the motor and sanding wheel, and eliminating noise and unnecessary wear on the gears.

Another object of the invention is the provision of an improved electric sanding machine which is adapted to operate with a substantial reduction in the amount of noise, and in which practically all of the undesirable rattling and grinding noises have been eliminated.

Another object of the invention is the provision of an improved electric sanding machine which is provided with an improved driving mechanism whereby the noise incident to its operation is transformed into a relatively smooth purr, as distinguished from growling, or slapping back and forth of the gears, which was incident to the operation of the devices of the prior art.

Another object of the invention is the provision of an improved electric sanding machine the violent grinding, i

having a simple metallic structure for permitting a floating action of the crown gear and sanding wheel with respect to the driving pinion so as to eliminate wear on the back of the teeth of the gears and to eliminate grinding and growling noises of the gears, and to improve the operating characteristics of the sanding machine.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the two sheets of drawings accompanying the specification,

Fig. 1 is a side elevational view of a sanding machine embodying the invention;

Fig. 2 is an enlarged fragmentary sectional View, drawn on a scale twice as large as one embodiment of the sanding machine, showing the structure of the mechanism;

Fig. 3 is a fragmentary sectional view, taken on the plane of the line 3-3 of Fig. 2, looking in the direction of the arrows.

Referring to Fig. 1, I0 indicates in its entirety an electric sanding machine, which is provided with an electric motor II, having a handle I2, and controlled by an electric switch in a switch box I3.

The motor is energized through the rubber covered insulated conductors I4, passing through the handle I2 into the motor II, and the motor I I has a substantially cylindrical housing, which is joined at the opposite end to a gear housing I5. Suitable slots I6 are provided between the motor housing Il and gear housing I5 for passage of the cooling and Ventilating air, which is drawn in at the slots I1, and which is impelled by centrifugal impeller I8 carried by the motor shaft I9 (Fig. 3).

The gear housing I5 is provided with a pair of laterally projecting lugs 20, having threaded bores 2l for the reception of a threaded member carried by a suitable handle 22, which may be mounted on either side of the gear housing for convenience in manipulation of the sander.

The gear housing I5 is also provided with a suitable supporting skid member 23, mounted on the side opposite from the sanding wheel for supporting the device when it is not in use.

Referring to Figs. 2 and 3, the gear housing I5 is preferably provided with a substantially cylindrical formation 24 adapted to be received in a complementary cylindrical chamber or opening 25 at the end of the motor housing II.

The gear housing I5 also has an annular shoulder 26, which fits against the end of the motor housing II, and the gear housing I5 may be secured in place by a plurality of through screw bolts (not shown), which extend through the motor housing II, and are threaded into the gear housing I5.

The gear housing I5 is provided with an inner chamber 21, which is adapted to receive lubricant, so that the gears may be surrounded by a bath of suitable semi-solid lubricant.

Chamber 21 is separated from the interior of the motor by an end partition 28, which may be provided with an inwardly extending socket formation 29, having the socket 30 for receiving the anti-friction bearing 3I, supporting the motor shaft I9.

The bearing socket 3U has an end wall 32, which terminates in a cylindrical opening 33, having a very limited clearance between the opening 33 and a steel baille disc 34 carried by the motor shaft I9. The close relation between the cylindrical 'periphery Yof the baille disc 34 and the aperture"33practicallyprevents the egress of 'the' ber lubricant from the" gear chamber l 21 into" the 'socket' 30 and into 'thefblower chamber I Ia. VAt the-'other side of the 'socket 3|, the partition 28 may be recessed at 35 to receive an oil sealingplate 36 ofjleather or other suitable flexible material, havingr aA` cylindrical aperture 31, enga'ging'av complementary cylindrical formation 38 on theshaft' I9. 'y l Thus the anti-friction bearing 3| may be provided with suitable lubricantof a different character from'th'at in' the gear`cha`1nber21g'but in any event, lubricant'is prevented from leaking into the motor'I I by the oil'seal'36.

The motor shaft I9 carries a pinion 39, having teethr4il, which are adapted to mesh'with the teeth 41 ofi aVv crown gear 42.A 'Crown gear 42 is mounted for free rotation on the hub 43 of a metal disc or y-wheel 44, which is carried by the driven shaft 45 and secured thereto by means of a key 46 and key-way41,'and recess 48.

The driven shaft 45 has a centralcylindrical portion 49 Vand a reduced threaded portion 59, and "a'reduced cylindrical portion 5I at its upper end (Fig. 2). The .nut 52 on the reduced threaded portion 50 engages the end of the 'hub 43 of the liywheel 44.

Irhe gear housing I5 is formed with a suitably located `cylindrical socket 53, having secured therein, by a pressed frictional fit, a sheet metal cage'54 of substantially cylindrical form. The cage 54 may havel its closed end 55 pressed inward,'forming an annular guide groove 55 at that end,`and the opposite end maybe turned over at 51 to form a second annular guide groove. A plurality of 'small roller bearings 58, provided with conical points at each end, have their pointed ends mounted in the guide grooves 56 and 5,1', to form a needle bearing.

Thel reduced cylindrical en'd 5I of the shaft 45 wis rotatably mounted inside the rollers58, which it is adapted to engage." 'j

The gear'housing'IS is provided at one side with an lopening bound by an innerfcylindrical wall 59, terminated at an annular shoulder 6I?. The annular shoulder 69, surrounding the opening 59, is'in a plane at right angles to the partition 28; This opening 59 is closed by Va cover plate 6I, having an outer cylindrical formation 62, fitting in the opening 59, and having an annular shoulder 63 engaging theannular shoulder 60. v

The cover plate 6I is provided with a centrally adjacent the inner race 66,

located cylindrical socket 64 for receiving the outer race 65 of an anti-friction bearing, which also includes the inner race 66 and a multiplicity of balls 61 mounted in the grooves 68, 69.

The anti-friction bearing is preferably of the thrust type, as shown, each of the grooves 68 and 69 being so arranged that they are adapted to hold the driven shaft 45 in its place, as well as to rotatably support the shaft.

The outer race 65 may support an oil seal plate 10 of metal, which has a very small clearance and practically prevents the egress of liber lubricant of the type used in the gear housing 21.

`.Balls 61 may be held in proper place by a suitable cage 1I.y The inner race 66 may engage a cylindrical formation 12 on the shaft 45, which is of larger size at this point. The shaft 45 has a reduced cylindrical portion 13, which carries a thrust member 14 that is secured to the shaft 45 by a key 15.

"Ring 14 is used with a pivoted latch member l'fto'hold the vshaft 45 in xed position, while a sa'nding'pad is attached to the shaft. yA spacer' collar"'I1y is interposed between the ring 1`4V and therace 66. *f

The shaft 45 is also provided with a still smaller cylindrical portion '18' andK a still smaller threaded portion 19,'V which is adapted to be received in the complementary threaded bore 80, located in the nut 8l of a disc-supporting pad, indicated in its entirety by 8 Thev disc-supporting pad may be of the type disclosed Ain'my prior Patent No. 2,132,917 for Abrasive devices, issued October 11, 1938, and it may carry suitable exible discs 83 and a sanding' disc 84.

'I'hey-wheel hub 43 has an extension 35 on the'lowerside of the hub'in Fig. 2, which is-pro` vided'with a" cylindrical peripheryv 66,1having a very small clearance with respect to a cylindrical bore 81'in a steel plate 88. The plate 88 is secured and an annular shoulder between the cover 6I 89,' and the cover 6I and plate 88are secured in place by a plurality of screw bolts IIa,'passing through the cover 6I andv threaded into the Vgear housing I5. i One of the most important features of the invention is the structure of the crown gear 42 and the yfiy-wheel 44; The crown gear 42 may cornprise'a vdisc-like metal member made of suitable hardened steel, having a cylindrical bore and having the laterally projecting teeth 4I arranged adjacent the cylindrical periphery 9I.

The bore 99 slidably receives the hub 43 so that the crown gear 42 is slidably mounted on the hub 43, but is restrained by the fact that its teeth 4I engage the teeth 4G of pinion 39. This prevents anything except a very limited amount of longitudinal motion of the crown gear 42 on A small Aamount of motion is permitted, to allow adjustment between the teeth'40 and Yto find the best driving relation.y I:[he fly-wheel 44 comprises a thick steel'disc, having -a substantially cylindrical-periphery 92, and having hat sides'93 and 94. `The iiy-wheel 44 is provided with a laterally projecting pin Vof cylindrical shape, which has one end xedly securedbya close frictional t in a bore 93 in the disc 44. The other end projects from the disc 44 and extends into-an enlarged cylindrical aperture 91 in the back side of the crown VgearA 42.

Referring to Fig. 3,'itwi1lbeffseen that there is a 'clearance 98 between the pin 95 and the bore The operation of the sanding machine, from the point of view of the sanding disc 84, is as follows: The motor, by means of its shaft I9, drives the pinion 39, which engages the crown gear 42 so that the crown gear 42 is driven at a reduced speed. The crown gear 42, through the pin 95 and socket 91, drives the disc 44, which drives the driven shaft 45 and the sanding disc 84.

The operation of the sanding machine, from the point of view of reduction in noise and wear on the teeth, is something for which it is difficult to find a logical explanation, but the applicants explanation of this phenomenon is as follows: It is a fact that this structure results in reduced wear on the gear teeth, particularly on the back side of the gears, and there is a marked difference in the characteristics of operation of the sanding machine. This difference is particularly noted in the reduction of noise, as the slapping and grinding of gears and the rattling of gears have been practically eliminated, and the grinding machine operates under load and without load with a sound which may be described as a purring action.

As all of the elements used in the drive are of metallic nature and may be made of steel, the present device is more durable than devices which I have heretofore employed for the purpose of reduction of noise and strain on the gears, and the present device may be operated for long periods of time without necessity for repair. I explain the operation of the mechanism as follows, but the present explanation is not necessarily the only one, and it may be found that there is some better explanation of the action of the mechanism.

The crown gear has the capability of moving a slight amount in an angular manner in either direction relative to the fly-wheel or disc 44. This permits the crown gear to have a iioating action in between the driven shaft 45 and the driving pinion 39. There is necessarily a certain amount of slack between the driving of the motor and the driven shaft 45 of the sanding machine under all conditions because there is a necessary manufacturing clearance between the teeth of the two gears.

The distinct slap or growl which is caused by the back sides of the teeth running into each other in the devices of the prior art, may be analogous to the noise which occurs on a railway train with loose couplings, which jerk violently on starting or stopping of the train.

In the present invention, when the load on the sanding wheel is released, the crown gear does not immediately slap back against the teeth of the pinion with a sudden jar, but it comes up against the back side of the teeth with a floating action that permits the crown gear and pinion to come together and find their own point of contact without noise such as is caused in the devices of the prior art.

This may be partly due to the fly-wheel action of the disc 44, which tends to keep the drive shaft running at a constant rate of speed, instead of permitting the sanding wheel to run ahead of the motor and cause engagement of the back of the pinion teeth by the crown gear teeth when the load is released. It is a fact that the structure shown reduces and practically eliminates the slap and grind and growl of the gears under these conditions, and results in the smooth purring operation of the electric sanding machine.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an electric sanding machine, the combination of a driving motor having a shaft provided with a pinion, a driven shaft for supporting a rotatable sanding member, said driven shaft being provided with a crown gear engaging said pinion, and a metallic drive between said driven shaft and said crown gear, having a predetermined amount of clearance to permit a oating action of the crown gear when the load is removed from the sanding member, and a rotating inertia member carried by the shaft and tending to maintain the rotative speed of the crown gear to prevent back slap of the crown gear against its pinion.

2. In an electric sanding machine, a driving mechanism comprising a pinion carried by the motor shaft, a driven shaft for supporting a sanding member, bearings for supporting said driven shaft, a crown gear carried by said driven shaft, and having a limited rotation on said driven shaft, and interengaging means between said crown gear and driven shaft, and having a predetermined range of movement whereby the crown gear is permitted to have a floating action when the load changes on the driven shaft, said inter-connecting means including a metallic disclike rotatable member having a predetermined inertia tendency to maintain the rotation of the driven shaft.

3. In an electric sanding machine, the combination of a driving motor having a motor shaft provided with a pinion, a driven shaft for supporting a rotatable sanding member, bearing means carried by said machine for said driven shaft, said driven shaft being provided with a driven gear engaging said pinion, and said gear being mounted for rotation on said driven shaft, a fly wheel member iixedly secured to said driven shaft and having a laterally projecting pin engaging in an aperture in said gear, said pin and aperture having a predetermined amount of clearance to permit a floating action of the gear when the load is removed from the sanding member.

4. In an electric sanding machine, the combination of a driving motor having a shaft provided with a pinion, a driven shaft for supporting a rotatable sanding member, said driven shaft being provided with a crown gear engaging said pinion, a flywheel carried by said driven shaft, a gear rotatably mounted concentrically with said flywheel, and metallic drive means interconnecting said flywheel and said gear with a predetermined clearance to permit floating driving action by said gear when the load is removed from the sanding member.

5. In an electric sanding machine, the combination of a driving motor having a shaft provided with a pinion, a driven shaft for supporting a rotatable sanding member, said driven shaft being provided with a crown gear engaging said pinion, a metallic drive between said driven shaft and said crown gear, said metallic drive being spaced outwardly from said driven shaft and having a predetermined amount of clearance to permit a oating action of the crown gear when the load is removed from the sanding member, and a rotating inertia member carried by the shaft and by said shaft and having predetermined limitedv rotative movement with said crown gear, whereby the crown gear is permitted to have a floating action when the load changes on the driven shaft.

7. In an electric sanding machine, a driving mechanism comprising a pinion carried by the motor shaft, a driven shaft for supporting a sanding member, bearings for supporting said driven shaft, a metallic disc-like member having a predetermined inertia tendency carried by said driven shaft to maintain the rotation thereof, a crown gear carried by said driven shaft and having Iimited rotation on said driven shaft, the rotation thereof being limited by interengaging means mounted between said crown gear and said driven shaft. v

FRANS O. ALBERTSON. 

